Annual report pursuant to Section 13 and 15(d)

Shareholders' Equity, Stock Options and Net Income per Share - Stock Option Activity (Details)

v3.10.0.1
Shareholders' Equity, Stock Options and Net Income per Share - Stock Option Activity (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based compensation $ 10,549 $ 8,103 $ 8,334
Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at beginning of year (shares) 440 564 786
Granted (shares) 193 128 137
Exercise of stock options (in shares) (95) (206) (346)
Forfeited (shares) 0 (46) (13)
Outstanding at end of year (shares) 538 440 564
Exercisable at end of year 230 226 331
Weighted Average Outstanding at beginning of year (per share) $ 45 $ 41 $ 32
Weighted average exercise price for options granted in the period 62 48 44
Weighted average exercise price for options exercised in the period 41 35 24
Weighted average exercise price for options forfeited in the period 0 46 35
Weighted Average Outstanding at end of year (per share) 51 45 41
Weighted average exercise price for options exercisable at year end 45 42 37
Weighted-average fair value of options granted during the year (dollars per share) $ 16 $ 13 $ 12
Aggregate intrinsic value of options exercised $ 1,992 $ 3,569 $ 7,803
Average aggregate intrinsic value for options outstanding 4,550    
Average aggregate instrinsic value for exercisable options 3,439    
Share-based compensation 1,578 1,313 1,473
Tax benefit related to share-based compensation expense 398 $ 466 $ 546
Unrecognized compensation cost $ 3,128    
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition 2 years 2 months 11 days    
Exercise Price Range 36.90 thru 37.14 [Member] | Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at end of year (shares) 36    
Exercisable at end of year 36    
Weighted Average Outstanding at end of year (per share) $ 37.11    
Weighted average exercise price for options exercisable at year end 37.11    
Range of exercise price, lower range limit 36.90    
Range of exercise price, upper range limit $ 37.14    
Weighted average remaining contractual life 1 year 11 days    
Exercise Price Range 41.32 thru 44.90 [Member] | Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at end of year (shares) 135    
Exercisable at end of year 101    
Weighted Average Outstanding at end of year (per share) $ 43.39    
Weighted average exercise price for options exercisable at year end 43.33    
Range of exercise price, lower range limit 41.32    
Range of exercise price, upper range limit $ 44.90    
Weighted average remaining contractual life 3 years 6 months 11 days    
Exercise Price Range 45.34 thru 48.32 [Member] | Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at end of year (shares) 116    
Exercisable at end of year 42    
Weighted Average Outstanding at end of year (per share) $ 47.76    
Weighted average exercise price for options exercisable at year end 47.61    
Range of exercise price, lower range limit 45.34    
Range of exercise price, upper range limit $ 48.32    
Weighted average remaining contractual life 5 years 11 days    
Exercise Price Range 50.71 thru 53.73 [Member] | Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at end of year (shares) 53    
Exercisable at end of year 49    
Weighted Average Outstanding at end of year (per share) $ 51.13    
Weighted average exercise price for options exercisable at year end 50.95    
Range of exercise price, lower range limit 50.71    
Range of exercise price, upper range limit $ 53.73    
Weighted average remaining contractual life 3 years 4 months 11 days    
Exercise Price Range 57.18 thru 60.42 [Member] | Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at end of year (shares) 98    
Exercisable at end of year 2    
Weighted Average Outstanding at end of year (per share) $ 58.78    
Weighted average exercise price for options exercisable at year end 57.18    
Range of exercise price, lower range limit 57.18    
Range of exercise price, upper range limit $ 60.42    
Weighted average remaining contractual life 6 years 1 month 11 days    
Exercise Price Range 64.26 thru 64.26 [Member] | Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at end of year (shares) 100    
Weighted Average Outstanding at end of year (per share) $ 64.26    
Range of exercise price, lower range limit 64.26    
Range of exercise price, upper range limit $ 64.26    
Weighted average remaining contractual life 6 years 8 months 11 days    
Exercise Price Range 36.90 thru 64.26 [Member] | Employee Stock Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding at end of year (shares) 538    
Exercisable at end of year 230    
Weighted Average Outstanding at end of year (per share) $ 51.37    
Weighted average exercise price for options exercisable at year end 44.89    
Range of exercise price, lower range limit 36.90    
Range of exercise price, upper range limit $ 64.26    
Weighted average remaining contractual life 4 years 8 months 11 days